The following correction was printed in the Guardian's Corrections and clarifications column, Thursday 10 December 2009

The report below, described Lord Judge as "Britain's most senior judge". This is not a recognised designation. Lord Judge has seniority in the judiciary of England and Wales, serving as lord chief justice in that realm, as the article noted. The United Kingdom's most senior judge, according to the Ministry of Justice, is the president of the new supreme court – though even then, his is not the court of highest authority in Scottish criminal cases: that is Scotland's high court of justiciary.

Britain's most senior judge has warned his fellow judges that he cannot envisage any circumstances in which it would be "constitutionally possible or proper" for a court to make an order that gagged debate in parliament. His warning follows the Guardian's free speech victory last week when lawyers for the oil trading company Trafigura gave up their attempt to gag parliament over its dumping of toxic waste in Ivory Coast.

Lord Judge's remarks – which included a warning against the free use of "super-injunctions – come before a Commons debate on the affair tomorrow moved by the Liberal Democrat Evan Harris at which MPs are expected to voice continuing concerns at attempts by lawyers Carter-Ruck to use the courts to gag parliament.

Lord Judge, the lord chief justice of England and Wales, said that the absolute privilege for MPs to speak freely in parliament was a fundamental principle that had not come without a price being paid by former generations: some had fought and died to defend it. "It is a precious heritage that in my view should be vigorously defended and maintained by this generation," he said, speaking on the first anniversary of his appointment.

Judge said that he would need "some powerful persuasion indeed – and that is close to saying that I cannot envisage it –- that it would be constitutionally possible or proper for a court to make an order that might prevent or hinder or limit discussion of any topic in parliament, or any judge would intentionally frame an injunction that would have that effect. We do not use the words 'fundamental principle' very frequently, but this is a fundamental principle."

He said there were some circumstances in which parliament would not discuss live proceedings in court because it would interfere with the administration of justice. But that decision was taken in such sub judice cases by parliament itself, because it had chosen "in the public interest not to insist on its privileges", and not as a result of a court seeking to order it.

He would not concede that the Trafigura affair, during which the nature of the "super-injunction" gag became globally known through the social networking site Twitter, meant that a judge sitting in London could no longer enforce such a ban.

The lord chief justice acknowledged that rapidly changing technology was proving challenging for the courts, but insisted that a gagging order still legally bound the parties against whom it was made not to disclose its contents. If it could be shown that the order was breached by the defendant, then it was possible to bring an action for contempt to enforce it.

The lord chief justice conceded that if the banned information came from a different source, there would be a difficulty.

But he made clear that he believed that there were circumstances in which so-called "super-injunctions" – a second injunction which bans any disclosure of the fact that the original injunction has been made – were justified.

He quoted an example of a fraud ring in which it was essential to keep an asset-freezing order against one member secret from the rest so that they did not dispose of their assets or flee the country. But he stressed that such an order should "only be made if failing to make it would destroy the purpose of the injunction, or cause the very damage that the injunction was designed to avoid".

There also had to be an early opportunity for those who were subject to the injunction to challenge it in court.

The lord chief justice voiced concerns about London's reputation as the "libel capital of the world", saying he was not proud of the title: "We need to look closely at why it is called the libel capital of the world and if it is, we have to try to persuade parliament to change the law."

Judge also voiced concern about the lack of public confidence in the criminal justice system and criticised proposals from the director of public prosecutions, Keir Starmer, to take the expected cost of trials into account when deciding whether or not it was proportionate to prosecute someone for serious offences. But he also said that the media had a role in creating public confidence in the courts. There were 100,000 crown court cases every year and "from time to time there is no doubt that a judge makes a wrong decision. But in the vast overwhelming majority of cases that doesn't happen," he said.

On prison overcrowding and the crisis facing jails, the lord chief justice said it had been a long-standing principle that it was in order to pass a shorter sentence on an offender who was being sent to an overcrowded jail.